As an end mill with coolant holes equipped with such a plurality of bottom blades and such a plurality of coolant holes, for example, Japanese Registered Utility Model No. 3025383 suggests the following four-bladed ball end mill. In this end mill, coolant holes (fluid supply holes) are made open to tip flank faces of two bottom blades among four bottom blades (tip cutting blades) of the ball end mill, whereas in order to equally supply the coolant (fluid) to all the bottom blades, the bottom blades are formed at the tip portion along three or four chip discharge grooves (helical gashes), and number of coolant holes equal to that of the chip discharge grooves are respectively made open to the tip flank faces of the bottom blades.
Additionally, Japanese Patent No. 4409665 also described an end mill with coolant holes and four unequal bottom blades. The end mill has a pair of long bottom blades provided up to the vicinity of an axial center along a pair of first gashes symmetrically formed with respect to the axial center, and a pair of short bottom blades provided along second gashes formed so as to reach the first gashes from an outer peripheral portion symmetrically with respect to the axial center at the positions of 90° from the pair of long bottom blades around the axial center. The end mill also has fluid supply holes (coolant holes) which have a pair of openings that are open to flank faces of the pair of long bottom blades and which are provided to longitudinally pass through the end mill, and a pair of communication grooves provided so as to increase the communication area of the first gashes and the second gashes where ends on the side of the axial center intersect each other and so as to connect intersecting portions between the first gashes and the second gashes and openings of the coolant holes.